Method for preparing oxalic acid



sept 29, 1970 E. v. oBMoRNov ETAL 3,531,520

METHOD FOR PREPARING OXALIC ACID Filed Sept. 15, 1966 United States Patent O 3,531,520 METHOD FOR PREPARING OXALIC ACID Evgeny Vaslievich Obmornov, Ul. Komsomolskaya 36/ 14, kv. 20; Vladimir Gerasimovich Karetuik, Ul. Trudovye rezervu 44, kv. 6; Valery Ivanovich Koptelov, Ul. Trudovye rezervy 46/ 12, kv. 31; Natalya Alexandrovna Dosovitskaya, Ul. Pochtovaya 13, kv. 12; Zinaida Petrovna Koptelova, Ul. Trudovye rezervy 46/ 12, kv. 31; Galina Pavlovna Masalova, Ul. Komsomolskaya 36/14, kv. 106; Elim Izrailevich Dosovitsky, Ul. Pochtovaya 13, kv. 12; and Vera Nikolaevna Ostrovskaya, Ul. Komsomolskaya 36/14, kv. 41, all of Novomoskovsk, Tulskoi oblasti, U.S.S.R.

Filed Sept. 15, 1966, Ser. No. 579,700 Int. Cl. C07c 51/26 U.S. Cl. 260-531 3 Claims ABSTRACT F THE DISCLOSURE Oxalic acid is produced by oxidizing ethylene glycol with sulfuric and nitric acid in the presence of vanadium pentoxide at a temperature of 50-70 C.

This invention relates to a method for preparing oxalic acid.

A known method for the manufacture of oxalic acid comprises oxidizing sugar with a mixture of sulfuric and nitric acids in the presence of vanadium pentoxide as a catalyst.

Another known method for preparing oxalic acid cornprises oxidizing ethylene glycol in an alkaline solution by boiling same with potassium permanganate.

The disadvantage of the former method is that it necessitates the use of a valuable product, viz., sugar, while the yield of oxalic acid is insuiiiciently high, being only about 80 percent of the theoretical amount.

The second method also suffers from the disadvantage that oxalic acid is obtained in a low yield of 20 percent of the theoretical amount.

It is an object of this invention to provide a method for preparing oxalic acid from a less expensive starting material than heretofore.

Another object of the invention is to provide a method for preparing oxalic acid, which makes it possible to avoid the use of an expensive food product as a starting material.

Still another object of the invention is to provide a method for producing oxalic acid from ethylene glycol, a readily available product of the chemical industry.

Yet another object of the invention is to provide a method for producing oxalic acid in which the steps are simple, and hence, no elaborate processing equipment is required.

It is also an object of this invention to lower the cost of oxalic acid.

It is, therefore, the primary object of the present invention to provide a method for the manufacture of oxalic acid in high yield by the catalytic oxidation of ethylene glycol with a view to employing said method for the cornmercial production of oxalic acid, and thereby avoiding the use of expensive sugar.

This object of the present invention is accomplished by catalytically oxidizing ethylene glycol with a mixture containing 30 to 40 percent of sulfuric acid and 20 to 25 percent of nitric acid, at a temperature of from 50 t0 70 C., at a pressure of 10 to 30 mm. Hg in the presence of a catalyst, preferably vanadium pentoxide.

The catalytic oxidation of ethylene glycol in accordance lCe with the present method makes it possible to attain a yield of oxalic acid of not less than 93 percent of the theoretical amount.

In order to enable those skilled in the art to better understand the invention, the following example which makes reference to the accompanying drawing is given by way of illustration.

EXAMPLE An oxidizing mixture is charged in a quantity of 17.8- 18.7 t. (l2.5-l3.0 m) into a l5 m stainless steel reactor 2 provided with a conical bottom, a jacket and coils for heating and cooling with water, a draining device for discharging the reaction mass, and a frame stirrer r0- tating at 25 to 30 r.p.m. Said mixture is obtained by using the mother liquors resulting from filtration of the sus? pension which results from the foregoing operations to recover nitric acid in absorbing towers 7 where there occurs the absorption of the Oxides of nitrogen liberated in reactor 2 during oxidation of ethylene glycol.

Said mixture has the following compositions: nitric acid 20-25 percent, sulfuric acid 30-40 percent, vanadium pentoxde 0.001-0.l percent, oxalic acid (left in the liquor from foregoing operations) 3.8-7.0 percent.

After a vacuum of 10 to 30 mm. Hg has been achieved in reactor 2 (by means of an exhauster) and the oxidizing mixture has been heated (by passing hot water through the reactor jacket) to 5070 C., commercial ethylene glycol is added from batcher 1, the amount of ethylene glycol being l part by weight per 2.7 to 3.2 parts of nitric acid contained in the oxidizing mixture.

While ethylene glycol is being added, the temperature of the reaction mixture is maintained at 50 C. by removing the reaction heat through the jacket and coil.

When the process is complete, the reaction mass is cooled and the resulting suspension is transferred through the discharge opening to receiving tank 3, from whence the suspension passes to the filtering unit. The oxalic acid crystals which accumulate in centrifuges 4 are washed with steam condensate or distilled water.

The mother liquor from receiver 5 is transferred to receiver 6 of the nitric acid recovery stage, where it is sprayed into absorbing tower 7.

Although the present invention has been described with reference to a preferred embodiment, various changes and modifications may be made in carrying out the invention without departing from the spirit and scope thereof, as will readily be understood by those skilled in the art.

What is claimed is:

1. A method for preparing oxalic acid comprising reacting ethylene glycol with an oxidizing mixture containing from 30 to 40 percent of sulfuric acid and from 20 to 25 percent of nitric acid, in the presence of vanadium pentoxide as a catalyst at a temperature of 50 to 70 C.

2. A method according to claim 1 wherein reacting is effected at a pressure of 10-30 mm. Hg.

3. A method according to claim 1 wherein the vanadium pentoxide comprises 0.00l-0.l percent of the oxidizing mixture.

References Cited UNITED STATES PATENTS t LORRAINE A. WEINBERGER, Primary Examiner DENNIS E. STENZEL, Assistant Examiner 

